Effect of scanning the palate in anatomically variant maxillary arches on the accuracy of complete arch implant scans: An in vitro study.

Abstract

Statement of problem: Intraorally scanning the palate may affect the accuracy of digital implant scans depending on the maxillary arch anatomy (arch form, palatal vault depth) and the number of implants.

Purpose: The purpose of this in vitro study was to investigate the effect of scanning the palate on the accuracy of maxillary implant complete arch scans with 3 different palatal vault depths and 3 arch forms and also the number of implants.

Material and methods: A maxillary edentulous cast was scanned using a desktop scanner and imported into a computer aided design and computer aided manufacturing (CAD-CAM) software program to create a digital control model. That model was duplicated and modified to create different digital control models that differ in palate depth (shallow, medium, deep), arch form (ovoid, square, tapered), and number of implants (4 or 6). The 18 digital files were used to print 18 physical casts that were scanned using 2 different techniques - palate-less (UP) and palate stitching (SP) - using an intraoral scanner. Each scanning technique was repeated 7 times, and a total of 252 scans (SP and UP) were obtained from the models and superimposed over the corresponding original digital control using an industrial metrology software program to obtain trueness and precision values for each scanning technique according to the different variables. The Kruskal-Wallis test was used to detect the differences in trueness and precision among the experimental groups and with different variables.

Results: No significant association was found between the maxillary complete arch scanning technique (SP and UP) and the accuracy of implant complete arch maxillary digital scans (P=.167). Both scanning methods (SP and UP) were significantly different in trueness and precision when compared with the control group (P<.001). The accuracy between the scans was not affected by arch form or number of implants (P>.05). However, shallow complete arch maxillary scans were more accurate than medium depth scans (P<.001), although the difference was small.

Conclusions: When 3 different palatal depths, 3 different arch forms, 4 versus 6 implants, and SP versus UP scans were examined, none of these variables were found to affect the accuracy of maxillary complete arch digital scans.